WO2024090340A1 - 磁気記録媒体およびカートリッジ - Google Patents

磁気記録媒体およびカートリッジ Download PDF

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Publication number
WO2024090340A1
WO2024090340A1 PCT/JP2023/037983 JP2023037983W WO2024090340A1 WO 2024090340 A1 WO2024090340 A1 WO 2024090340A1 JP 2023037983 W JP2023037983 W JP 2023037983W WO 2024090340 A1 WO2024090340 A1 WO 2024090340A1
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WO
WIPO (PCT)
Prior art keywords
magnetic
less
recording medium
magnetic tape
magnetic recording
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2023/037983
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English (en)
French (fr)
Japanese (ja)
Inventor
実 山鹿
裕子 鴨下
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Sony Group Corp
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Sony Group Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sony Group Corp filed Critical Sony Group Corp
Priority to US19/113,131 priority Critical patent/US20260100199A1/en
Priority to JP2024553016A priority patent/JPWO2024090340A1/ja
Publication of WO2024090340A1 publication Critical patent/WO2024090340A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/78—Tape carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B21/00—Head arrangements not specific to the method of recording or reproducing
    • G11B21/02—Driving or moving of heads
    • G11B21/10—Track finding or aligning by moving the head ; Provisions for maintaining alignment of the head relative to the track during transducing operation, i.e. track following
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
    • G11B23/02—Containers; Storing means both adapted to cooperate with the recording or reproducing means
    • G11B23/04—Magazines; Cassettes for webs or filaments
    • G11B23/08—Magazines; Cassettes for webs or filaments for housing webs or filaments having two distinct ends
    • G11B23/107—Magazines; Cassettes for webs or filaments for housing webs or filaments having two distinct ends using one reel or core, one end of the record carrier coming out of the magazine or cassette
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/584—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on tapes
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70626—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
    • G11B5/70642—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides
    • G11B5/70678—Ferrites
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/714—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the dimension of the magnetic particles
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/736—Non-magnetic layer under a soft magnetic layer, e.g. between a substrate and a soft magnetic underlayer [SUL] or a keeper layer
    • G11B5/7367—Physical structure of underlayer, e.g. texture
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers

Definitions

  • This disclosure relates to a magnetic recording medium and a cartridge equipped with the same.
  • Patent Document 1 describes that when the arithmetic mean roughness Ra of the surface on the magnetic layer side is 2.5 nm or less, excellent SNR (electromagnetic conversion characteristics) can be obtained.
  • the objective of this disclosure is to provide a magnetic recording medium capable of obtaining excellent electromagnetic conversion characteristics and a cartridge equipped with the same.
  • the magnetic recording medium of the present disclosure comprises: A tape-shaped magnetic recording medium, A substrate and a magnetic layer are provided, The average thickness of the magnetic recording medium is 5.30 ⁇ m or less;
  • the magnetic recording medium of the present disclosure includes: A tape-shaped magnetic recording medium, A substrate and a magnetic layer are provided, The average thickness of the magnetic recording medium is 5.30 ⁇ m or less;
  • the cartridge according to the present disclosure includes any one of the above magnetic recording media according to the present disclosure.
  • FIG. 1 is an exploded perspective view illustrating an example of a configuration of a cartridge according to an embodiment of the present disclosure.
  • FIG. 2 is a block diagram showing an example of the configuration of the cartridge memory.
  • FIG. 3 is a cross-sectional view showing an example of the structure of a magnetic tape.
  • FIG. 4 is a schematic diagram showing an example of a layout of a data band and a servo band.
  • FIG. 5 is an enlarged view showing an example of the configuration of a data band.
  • FIG. 6 is an enlarged view showing an example of the configuration of a servo band.
  • FIG. 7 is a perspective view showing an example of the shape of a particle.
  • FIG. 8 is a diagram showing a first example of a cross-sectional TEM image of the magnetic layer.
  • FIG. 9 is a diagram showing a second example of a cross-sectional TEM image of the magnetic layer.
  • FIG. 10 is a diagram for explaining the relationship between the unevenness on the surface on the magnetic layer side, and the ratio of integrated values of power spectral densities I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 and kurtosis Sku.
  • FIG. 11 is a graph showing an example of a power spectral density obtained by analyzing a two-dimensional surface profile.
  • FIG. 12 is a diagram showing how powder generated by scraping off a protrusion spreads.
  • FIG. 13 is an exploded perspective view showing an example of a configuration of a cartridge according to a modified example of an embodiment of the present disclosure.
  • Cartridge structure 2. Cartridge memory structure 3. Magnetic tape structure 4. Magnetic tape manufacturing method 5. Functions and effects 6. Modifications
  • the measurements and evaluations are performed in an environment of 25°C ⁇ 2°C and 50% RH ⁇ 5% RH.
  • FIG. 1 is an exploded perspective view showing an example of the configuration of a cartridge 10.
  • the cartridge 10 is a one-reel type cartridge, and includes, inside a cartridge case 12 consisting of a lower shell 12A and an upper shell 12B, one reel 13 on which a tape-like magnetic recording medium (hereinafter referred to as "magnetic tape") MT is wound, a reel lock 14 and a reel spring 15 for locking the rotation of the reel 13, a spider 16 for unlocking the locked state of the reel 13, a slide door 17 for opening and closing a tape outlet 12C provided in the cartridge case 12 across the lower shell 12A and the upper shell 12B, a door spring 18 for biasing the slide door 17 to a closed position of the tape outlet 12C, a write protect 19 for preventing erroneous erasure, and a cartridge memory 11.
  • magnetic tape tape-like magnetic recording medium
  • the reel 13 for winding the magnetic tape MT is substantially disc-shaped with an opening in the center, and is composed of a reel hub 13A and a flange 13B made of a hard material such as plastic.
  • a leader tape LT is connected to the outer peripheral end of the magnetic tape MT, and a leader pin 20 is provided at the tip of the leader tape LT.
  • the cartridge 10 may be a magnetic tape cartridge that conforms to the LTO (Linear Tape-Open) standard, or it may be a magnetic tape cartridge that conforms to a standard other than the LTO standard.
  • LTO Linear Tape-Open
  • the cartridge memory 11 is provided near one corner of the cartridge 10. When the cartridge 10 is loaded into the recording and playback device, the cartridge memory 11 faces the reader/writer of the recording and playback device.
  • the cartridge memory 11 communicates with the recording and playback device, specifically the reader/writer, using a wireless communication standard that complies with the LTO standard.
  • the cartridge memory 11 includes an antenna coil (communication unit) 31 that communicates with a reader/writer using a prescribed communication standard, a rectification/power circuit 32 that generates power from radio waves received by the antenna coil 31 using induced electromotive force and rectifies the power to generate power, a clock circuit 33 that generates a clock from the radio waves received by the antenna coil 31 using induced electromotive force, a detection/modulation circuit 34 that detects the radio waves received by the antenna coil 31 and modulates the signal to be transmitted by the antenna coil 31, a controller (control unit) 35 consisting of a logic circuit for determining commands and data from the digital signal extracted from the detection/modulation circuit 34 and processing the commands and data, and a memory (storage unit) 36 that stores information.
  • the cartridge memory 11 also includes a capacitor 37 connected in parallel to the antenna coil 31, and the antenna coil 31 and the capacitor 37 form a resonant circuit.
  • Memory 36 stores information related to cartridge 10.
  • Memory 36 is non-volatile memory (NVM).
  • the storage capacity of memory 36 is preferably approximately 32 KB or more.
  • the memory 36 may have a first memory area 36A and a second memory area 36B.
  • the first memory area 36A corresponds to the memory area of a cartridge memory of a magnetic tape standard prior to the specified generation (e.g., an LTO standard prior to LTO8), for example, and is an area for storing information conforming to the magnetic tape standard prior to the specified generation.
  • Information conforming to the magnetic tape standard prior to the specified generation is, for example, manufacturing information (e.g., a unique number for the cartridge 10), usage history (e.g., the number of times the tape has been pulled out (Thread Count)), etc.
  • the second memory area 36B corresponds to an extended memory area for the memory area of the cartridge memory of the magnetic tape standard before the specified generation (for example, the LTO standard before LTO8).
  • the second memory area 36B is an area for storing additional information.
  • the additional information means, for example, information related to the cartridge 10 that is not specified in the magnetic tape standard before the specified generation (for example, the LTO standard before LTO8).
  • the additional information includes, for example, at least one type of information selected from the group consisting of tension adjustment information, management ledger data, index information, and thumbnail information, but is not limited to these data.
  • the tension adjustment information is information for adjusting the tension applied in the longitudinal direction of the magnetic tape MT.
  • the tension adjustment information includes, for example, at least one type of information selected from the group consisting of information obtained by intermittently measuring the width between the servo bands in the longitudinal direction of the magnetic tape MT, tension information of the drive, and information on the temperature and humidity of the drive. These pieces of information may be managed in conjunction with information on the usage status of the cartridge 10. It is preferable that the tension adjustment information is obtained when data is recorded on the magnetic tape MT or before data is recorded.
  • Drive tension information refers to information about the tension applied to the magnetic tape MT in the longitudinal direction.
  • the management ledger data includes at least one type of data selected from the group consisting of the capacity, creation date, editing date, and storage location of the data file recorded on the magnetic tape MT.
  • the index information is metadata for searching the contents of the data file.
  • the thumbnail information is a thumbnail of the video or still image stored on the magnetic tape MT.
  • Memory 36 may have multiple banks. In this case, some of the multiple banks may form a first memory area 36A, and the remaining banks may form a second memory area 36B.
  • the antenna coil 31 induces an induced voltage by electromagnetic induction.
  • the controller 35 communicates with the recording and playback device via the antenna coil 31 using a specified communication standard. Specifically, for example, it performs mutual authentication, sending and receiving commands, and exchanging data.
  • the controller 35 stores information received from the recording and playback device via the antenna coil 31 in the memory 36.
  • the controller 35 stores tension adjustment information received from the recording and playback device via the antenna coil 31 in the second memory area 36B of the memory 36.
  • the controller 35 reads information from the memory 36 and transmits it to the recording and playback device via the antenna coil 31.
  • the controller 35 reads tension adjustment information from the second memory area 36B of the memory 36 and transmits it to the recording and playback device via the antenna coil 31.
  • the magnetic tape MT includes a long substrate 41, an underlayer 42 provided on one main surface (first main surface) of the substrate 41, a magnetic layer 43 provided on the underlayer 42, and a back layer 44 provided on the other main surface (second main surface) of the substrate 41.
  • the underlayer 42 and the back layer 44 are provided as necessary and may not be required.
  • the magnetic tape MT may be a perpendicular recording type magnetic recording medium or a longitudinal recording type magnetic recording medium. From the viewpoint of improving running performance, the magnetic tape MT preferably contains a lubricant.
  • the lubricant may be included in at least one layer of the underlayer 42 and the magnetic layer 43.
  • the magnetic tape MT may be one that complies with the LTO standard, or one that complies with a standard other than the LTO standard.
  • the width of the magnetic tape MT may be 1/2 inch, or may be wider than 1/2 inch. If the magnetic tape MT complies with the LTO standard, the width of the magnetic tape MT is 1/2 inch.
  • the magnetic tape MT may have a configuration that allows the width of the magnetic tape MT to be kept constant or nearly constant by adjusting the tension applied to the magnetic tape MT in the longitudinal direction during running using a recording/playback device (drive).
  • the magnetic tape MT is long and runs in the longitudinal direction during recording and playback.
  • the magnetic tape MT is preferably used in a recording and playback device equipped with a ring-type head as a recording head.
  • the magnetic tape MT is preferably used in a recording and playback device configured to be able to record data with a data track width of 1200 nm or less or 1000 nm or less.
  • the magnetic tape MT is preferably reproduced by a reproduction head using a TMR element.
  • the signal reproduced by the reproduction head using TMR may be data recorded in the data band DB (see FIG. 4) or a servo pattern (servo signal) recorded in the servo band SB (see FIG. 4).
  • the substrate 41 is a non-magnetic support that supports the underlayer 42 and the magnetic layer 43.
  • the substrate 41 has a long film shape.
  • the upper limit of the average thickness of the substrate 41 is preferably 4.40 ⁇ m or less, more preferably 4.20 ⁇ m or less, even more preferably 4.00 ⁇ m or less, particularly preferably 3.80 ⁇ m or less, and most preferably 3.40 ⁇ m or less.
  • the lower limit of the average thickness of the substrate 41 is preferably 3.00 ⁇ m or more, more preferably 3.20 ⁇ m or more. When the lower limit of the average thickness of the substrate 41 is 3.00 ⁇ m or more, the strength reduction of the substrate 41 can be suppressed.
  • the average thickness of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT to a length of 250 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT.
  • longitudinal direction when referring to "the longitudinal direction from one end of the outer periphery of the magnetic tape MT” means the direction from one end of the outer periphery of the magnetic tape MT toward the other end of the inner periphery.
  • the layers of the sample other than the substrate 41 i.e., the underlayer 42, the magnetic layer 43, and the back layer 44
  • a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • the thickness of the sample (substrate 41) is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the average thickness of the substrate 41 is calculated by simply averaging (arithmetic mean) these measurements. Note that the five measurement positions are selected randomly from the sample so that they are each different positions in the longitudinal direction of the magnetic tape MT.
  • the base 41 contains, for example, a polyester-based resin as a main component.
  • the polyester-based resin contains, for example, at least one selected from the group consisting of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p(oxybenzoate), and polyethylene bisphenoxycarboxylate).
  • PET polyethylene terephthalate
  • PEN polyethylene naphthalate
  • PBT polybutylene terephthalate
  • PBN polybutylene naphthalate
  • PCT polycyclohexylene dimethylene terephthalate
  • PEB polyethylene-p(oxybenzoate
  • polyethylene bisphenoxycarboxylate polyethylene bisphenoxycarboxylate
  • the term "main component” means the component that is contained in the highest proportion among the components that constitute the base 41.
  • the content of the polyester-based resin in the base 41 may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more relative to the mass of the base 41, or the base 41 may be composed only of a polyester-based resin.
  • the substrate 41 contains polyester-based resin can be confirmed, for example, as follows. First, similar to the method for measuring the average thickness of the substrate 41, a magnetic tape MT is prepared and cut to a length of 250 mm to prepare a sample, and then the layers of the sample other than the substrate 41 are removed. Next, an IR spectrum of the sample (substrate 41) is obtained by infrared absorption spectrometry (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains polyester-based resin.
  • IR infrared absorption spectrometry
  • the substrate 41 preferably contains a polyester-based resin.
  • the Young's modulus in the longitudinal direction of the substrate 41 can be reduced to preferably 2.5 GPa or more and 7.8 GPa or less, more preferably 3.0 GPa or more and 7.0 GPa or less. Therefore, by adjusting the tension in the longitudinal direction of the magnetic tape MT during running using a recording/playback device, the width of the magnetic tape MT can be kept constant or nearly constant. A method for measuring the Young's modulus in the longitudinal direction of the substrate 41 will be described later.
  • the base 41 may contain a resin other than polyester-based resin.
  • the resin other than polyester-based resin may be the main component of the constituent material of the base 41.
  • the content ratio of the resin other than polyester-based resin in the base 41 may be, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 98 mass% or more relative to the mass of the base 41, or the base 41 may be composed only of a resin other than polyester-based resin.
  • the resin other than polyester-based resin includes, for example, at least one selected from the group consisting of polyolefin-based resins, cellulose derivatives, vinyl-based resins, and other polymer resins.
  • the base 41 contains two or more of these resins, the two or more materials may be mixed, copolymerized, or laminated.
  • the polyolefin resin includes, for example, at least one selected from the group consisting of PE (polyethylene) and PP (polypropylene).
  • the cellulose derivative includes, for example, at least one selected from the group consisting of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).
  • the vinyl resin includes, for example, at least one selected from the group consisting of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).
  • polymer resins include, for example, at least one selected from the group consisting of PEEK (polyetheretherketone), PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, e.g.
  • Zylon (registered trademark)), polyether, PEK (polyetherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).
  • the base 41 may contain PEEK (polyetheretherketone), PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, for example Zylon (registered trademark)), polyether, PEK (polyetherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), or PU (polyurethane) as a main component.
  • PEEK polyetheretherketone
  • PA polyamide, nylon
  • aromatic PA aromatic polyamide, aramid
  • PI polyimide
  • PAI polyamideimide
  • PAI aromatic PAI (aromatic polyamideimide)
  • PBO poly
  • the substrate 41 may be biaxially stretched in the longitudinal and width directions.
  • the polymer resin contained in the substrate 41 is preferably oriented in a direction oblique to the width direction of the substrate 41.
  • the magnetic layer 43 is configured to be capable of recording signals by a magnetization pattern.
  • the magnetic layer 43 may be a perpendicular recording type recording layer or a longitudinal recording type recording layer.
  • the magnetic layer 43 includes, for example, magnetic particles and a binder.
  • the magnetic layer 43 may further include at least one additive selected from the group consisting of conductive particles, abrasive particles, lubricants, hardeners, rust inhibitors, and non-magnetic reinforcing particles, as necessary.
  • the magnetic layer 43 may have a plurality of protrusions 430 on the surface on the magnetic layer 43 side (hereinafter referred to as the "magnetic surface").
  • the plurality of protrusions 430 are formed, for example, by conductive particles and abrasive particles protruding from the magnetic surface.
  • the magnetic layer 43 may already have a plurality of servo bands SB and a plurality of data bands DB, as shown in FIG. 4.
  • the plurality of servo bands SB are arranged at equal intervals in the width direction of the magnetic tape MT.
  • a data band DB is provided between adjacent servo bands SB.
  • the servo bands SB are for guiding the head unit (magnetic head) 56 (specifically, servo read heads 56A, 56B) when recording or reproducing data.
  • a servo pattern (servo signal) for tracking control of the head unit 56 is written in advance in the servo bands SB. User data is recorded in the data bands DB.
  • the head unit 56 may be configured to be able to maintain an angle with respect to an axis Ax parallel to the width direction of the magnetic tape MT when recording and reproducing data, as shown in FIG. 4.
  • the head unit 56 may be configured to follow the meandering or deformation of the magnetic tape MT and become angled with respect to the axis Ax when recording and reproducing data.
  • the inclination angle of the head unit 56 with respect to the axis Ax parallel to the width direction of the magnetic tape MT is preferably 3° to 18°, more preferably 5° to 15°.
  • the lower limit of the ratio R S of the total area S SB of the plurality of servo bands SB to the area S of the magnetic surface is preferably 1.0% or more, from the viewpoint of ensuring 5 or more servo bands SB.
  • the ratio R S of the total area S SB of the servo bands SB to the area S of the entire magnetic surface is calculated as follows:
  • the magnetic tape MT is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and the developed magnetic tape MT is then observed under an optical microscope to measure the servo band width W SB and the number of servo bands SB.
  • the number of servo bands SB is, for example, 5+4n or more (where n is an integer equal to or greater than 0).
  • the number of servo bands SB is preferably 5 or more, and more preferably 9 or more. If the number of servo bands SB is 5 or more, the effect of dimensional changes in the width direction of the magnetic tape MT on the servo signal can be suppressed, ensuring stable recording and playback characteristics with less off-track.
  • the upper limit of the number of servo bands SB is not particularly limited, but is, for example, 33 or less.
  • the number of servo bands SB is calculated in the same manner as the ratio RS described above.
  • the upper limit of the servo band width WSB is preferably 95 ⁇ m or less, more preferably 65 ⁇ m or less, and even more preferably 50 ⁇ m or less.
  • the lower limit of the servo band width WSB is preferably 10 ⁇ m or more. It is difficult to manufacture a magnetic head capable of reading a servo signal with a servo band width WSB of less than 10 ⁇ m.
  • the width of the servo band width WSB is calculated in the same manner as the ratio RS described above.
  • the magnetic layer 43 is configured to allow multiple data tracks Tk to be formed in the data band DB.
  • the upper limit of the data track width W is preferably 1200 nm or less, 1000 nm or less, 850 nm or less, or 800 nm or less, and particularly preferably 600 nm or less.
  • the lower limit of the data track width W is preferably 20 nm or more.
  • the data track width W is obtained as follows. First, a cartridge 10 with data recorded on the entire surface of the magnetic tape MT is prepared, the magnetic tape MT is unwound from the cartridge 10, and the magnetic tape MT is cut into a length of 250 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT to prepare a sample. Next, the data recording pattern of the data band DB part of the magnetic layer 43 of the sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. As the MFM, Dimension3100 manufactured by Digital Instruments and its analysis software are used.
  • MFM Magnetic force microscope
  • the analysis software provided with the Dimension3100 is used to measure the track width.
  • the measurement conditions for the above MFM are sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.
  • the magnetic layer 43 is configured to be capable of recording data such that the minimum distance Lmin between magnetization reversals is preferably 47 nm or less, more preferably 44 nm or less, even more preferably 42 nm or less, and particularly preferably 40 nm or less.
  • the lower limit of the minimum distance Lmin between magnetization reversals is preferably 20 nm or more.
  • MFM magnetic force microscope
  • bit distances are measured from a two-dimensional concave-convex chart of the recording pattern of the obtained MFM image.
  • the measurement of the bit distance is performed using analysis software attached to Dimension3100.
  • the minimum distance between magnetization reversals Lmin is determined as the approximate greatest common divisor of the 50 measured distances between bits.
  • the measurement conditions are sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.
  • the bit length L bit of the signal recorded in the data band DB is preferably 47 nm or less or 46 nm or less, more preferably 44 nm or less, even more preferably 42 nm or less, and particularly preferably 40 nm or less.
  • the bit length L bit of the signal recorded in the data band DB is determined in the same manner as the method for measuring the minimum value L min of the distance between magnetic reversals.
  • the bit area of the signal recorded in the data band DB is preferably 53,000 nm2 or less, more preferably 45,000 nm2 or less, even more preferably 37,000 nm2 or less, and particularly preferably 30,000 nm2 or less.
  • the bit area of the signal recorded in the data band DB is calculated as follows. First, three MFM images are obtained in the same manner as in the method for measuring the data track width W. Next, the data track width W and the bit length L bit are calculated in the same manner as in the method for measuring the data track width W and the bit length L bit . Next, the bit area (W ⁇ L bit ) of the signal recorded in the data band DB is calculated using the data track width W and the bit length L bit .
  • the servo pattern is a magnetized region, and is formed by magnetizing a specific region of the magnetic layer 43 in a specific direction with a servo write head during magnetic tape manufacturing.
  • the region of the servo band SB where the servo pattern is not formed (hereinafter referred to as the "non-pattern region") may be a magnetized region where the magnetic layer 43 is magnetized, or a non-magnetized region where the magnetic layer 43 is not magnetized.
  • the non-pattern region is a magnetized region
  • the servo pattern forming region and the non-pattern region are magnetized in different directions (e.g., opposite directions).
  • the servo band SB has a servo pattern formed thereon consisting of multiple servo stripes (linear magnetized regions) 113 inclined with respect to an axis Ax parallel to the width direction of the magnetic tape MT, as shown in FIG. 6.
  • the servo band SB includes multiple servo frames 110.
  • Each servo frame 110 is made up of 18 servo stripes 113.
  • each servo frame 110 is made up of a servo subframe 1 (111) and a servo subframe 2 (112).
  • Servo subframe 1 is composed of an A burst 111A and a B burst 111B.
  • the B burst 111B is disposed adjacent to the A burst 111A.
  • the A burst 111A has five servo stripes 113 formed at regular intervals and inclined at a predetermined angle ⁇ 1 with respect to an axis Ax parallel to the width direction of the magnetic tape MT. In Fig. 6, these five servo stripes 113 are indicated by the symbols A1 , A2 , A3 , A4 , and A5 from the EOT (End Of Tape) to the BOT (Beginning Of Tape) of the magnetic tape MT.
  • the B burst 111B has five servo stripes 113 formed at regular intervals and inclined at a predetermined angle ⁇ 2 with respect to an axis Ax parallel to the width direction of the magnetic tape MT.
  • these five servo stripes 113 are indicated by the symbols B1 , B2 , B3 , B4 , and B5 from the EOT to the BOT of the magnetic tape MT.
  • the servo stripes 113 of B burst 111B are inclined in the opposite direction to the servo stripes 113 of A burst 111A.
  • the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are asymmetric with respect to the axis Ax parallel to the width direction of the magnetic tape MT. In other words, the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are arranged in a roughly V-shape.
  • the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are asymmetric with respect to the axis Ax, when the head unit 56 is inclined obliquely with respect to the axis Ax, there exists a state in which the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are roughly symmetric with respect to the central axis of the sliding surface of the head unit 56.
  • By changing the inclination of the head unit 56 based on this state it becomes possible to adjust the distance between the servo read heads 56A, 56B in the width direction of the magnetic tape MT.
  • the servo read heads 56A, 56B can be made to face the specified positions of the servo band SB.
  • the central axis of the sliding surface of the head unit 56 means the axis that passes through the centers of the multiple servo read heads 56A, 56B on the sliding surface of the head unit 56.
  • the predetermined angle ⁇ 1 which is the inclination angle of the servo stripes 113 of the A burst 111A is different from the predetermined angle ⁇ 2 which is the inclination angle of the servo stripes 113 of the B burst 111B. More specifically, the predetermined angle ⁇ 1 of the servo stripes 113 of the A burst 111A may be larger than the predetermined angle ⁇ 2 of the servo stripes 113 of the B burst 111B, or the predetermined angle ⁇ 2 of the servo stripes 113 of the B burst 111B may be larger than the predetermined angle ⁇ 1 of the servo stripes 113 of the A burst 111A.
  • the inclination of the servo stripes 113 of the A burst 111A may be larger than the inclination of the servo stripes 113 of the B burst 111B, or the inclination of the servo stripes 113 of the B burst 111B may be larger than the inclination of the servo stripes 113 of the A burst 111A.
  • 6 shows an example in which the predetermined angle ⁇ 1 of the servo stripe 113 of the A burst 111A is larger than the predetermined angle ⁇ 2 of the servo stripe 113 of the B burst 111B.
  • Servo subframe 2 (112) is composed of a C burst 112C and a D burst 112D.
  • the D burst 112D is disposed adjacent to the C burst 112C.
  • the C burst 112C has four servo stripes 113 formed at a specified interval and inclined at a specified angle ⁇ 1 with respect to an axis Ax parallel to the width direction of the magnetic tape MT. In Fig. 6, these four servo stripes 113 are indicated by the symbols C1 , C2 , C3 , and C4 from the EOT to the BOT of the magnetic tape MT.
  • the D burst 112D has four servo stripes 113 formed at regular intervals and inclined at a predetermined angle ⁇ 2 with respect to an axis Ax parallel to the width direction of the magnetic tape MT.
  • these four servo stripes 113 are indicated by the symbols D1 , D2 , D3 , and D4 from the EOT to the BOT of the magnetic tape MT.
  • the servo stripes 113 of the D burst 112D are inclined in the opposite direction to the servo stripes 113 of the C burst 112C.
  • the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are asymmetric with respect to the axis Ax parallel to the width direction of the magnetic tape MT. That is, the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are arranged in a substantially V-shape.
  • the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are asymmetric with respect to the axis Ax, when the head unit 56 is inclined obliquely with respect to the axis Ax, there exists a state in which the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are substantially symmetric with respect to the central axis of the head unit 56. By changing the inclination of the head unit 56 based on this state, it becomes possible to adjust the servo distance.
  • the predetermined angle ⁇ 1 which is the inclination angle of the servo stripes 113 of the C burst 112C is different from the predetermined angle ⁇ 2 which is the inclination angle of the servo stripes 113 of the D burst 112D. More specifically, the predetermined angle ⁇ 1 of the servo stripes 113 of the C burst 112C may be larger than the predetermined angle ⁇ 2 of the servo stripes 113 of the D burst 112D, or the predetermined angle ⁇ 2 of the servo stripes 113 of the D burst 112D may be larger than the predetermined angle ⁇ 1 of the servo stripes 113 of the C burst 112C.
  • the inclination of the servo stripes 113 of the C burst 112C may be larger than the inclination of the servo stripes 113 of the D burst 112D, or the inclination of the servo stripes 113 of the D burst 112D may be larger than the inclination of the servo stripes 113 of the C burst 112C.
  • 6 shows an example in which the predetermined angle ⁇ 1 of the servo stripe 113 of the C burst 112C is larger than the predetermined angle ⁇ 2 of the servo stripe 113 of the D burst 112D.
  • the predetermined angle ⁇ 1 of the servo stripes 113 in the A burst 111A and the C burst 112C is preferably 18° or more and 28° or less, more preferably 18° or more and 26° or less.
  • the predetermined angle ⁇ 2 of the servo stripes 113 in the B burst 111B and the D burst 112D is preferably -4° or more and 6° or less, more preferably -2° or more and 6° or less.
  • the servo stripes 113 in the A burst 111A and the C burst 112C are an example of a first magnetized region.
  • the servo stripes 113 in the B burst 111B and the D burst 112D are an example of a second magnetized region.
  • the servo band SB is read by the head unit 56 to obtain information for obtaining the tape speed and the vertical position of the head unit 56.
  • the tape speed is calculated from the time between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4).
  • the head position is calculated from the time between the aforementioned four timing signals and the time between another four timing signals (A1-B1, A2-B2, A3-B3, A4-B4).
  • the servo pattern may be a shape that includes two parallel lines.
  • the servo pattern (i.e., the multiple servo stripes 113) is preferably arranged linearly in the longitudinal direction of the magnetic tape MT.
  • the servo band SB is preferably linear in the longitudinal direction of the magnetic tape MT.
  • the upper limit of the average thickness t1 of the magnetic layer 43 is preferably 0.08 ⁇ m or less, more preferably 0.065 ⁇ m or less, and even more preferably 0.055 ⁇ m or less. If the upper limit of the average thickness t1 of the magnetic layer 43 is 0.08 ⁇ m or less, when a ring-type head is used as the recording head, the influence of the demagnetizing field can be reduced, and further excellent electromagnetic conversion characteristics can be obtained.
  • the lower limit of the average thickness t1 of the magnetic layer 43 is preferably 0.035 ⁇ m or more. If the lower limit of the average thickness t1 of the magnetic layer 43 is 0.035 ⁇ m or more, output can be ensured when an MR head is used as the reproducing head, and therefore further excellent electromagnetic conversion characteristics can be obtained.
  • the average thickness t1 of the magnetic layer 43 is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out to a length of 250 mm from each of the positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from one end of the outer periphery of the magnetic tape MT in the longitudinal direction to prepare three samples. Then, each sample is processed by the FIB method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as a protective film as a pretreatment for observing a TEM image of a cross section described later.
  • the carbon layer is formed on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side by a vapor deposition method, and the tungsten layer is further formed on the surface on the magnetic layer 43 side by a vapor deposition method or a sputtering method.
  • the thinning is performed along the longitudinal direction of the magnetic tape MT. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.
  • the thickness of the magnetic layer 43 is measured at 10 positions of each of the thin samples.
  • the measurement positions of the 10 points of each of the thin samples are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.
  • the average value obtained by simply averaging (arithmetic mean) the measured values of each of the obtained thin samples (a total of 30 thicknesses of the magnetic layer 43) is set as the average thickness t 1 [nm] of the magnetic layer 43.
  • the magnetic particles are, for example, particles containing hexagonal ferrite (hereinafter referred to as “hexagonal ferrite particles”), particles containing epsilon iron oxide ( ⁇ iron oxide) (hereinafter referred to as “ ⁇ iron oxide particles”), or particles containing Co-containing spinel ferrite (hereinafter referred to as “cobalt ferrite particles”). It is preferable that the magnetic particles have a crystal orientation preferentially in the perpendicular direction of the magnetic tape MT. In this specification, the perpendicular direction (thickness direction) of the magnetic tape MT means the thickness direction of the magnetic tape MT in a flat state.
  • the hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate shape or a column shape such as a hexagonal column shape (however, the thickness or height is smaller than the major axis of the plate surface or bottom surface).
  • the hexagonal plate shape includes a substantially hexagonal plate shape.
  • the hexagonal ferrite preferably contains at least one selected from the group consisting of Ba, Sr, Pb, and Ca, more preferably at least one selected from the group consisting of Ba and Sr.
  • the hexagonal ferrite may be, for example, barium ferrite or strontium ferrite.
  • the barium ferrite may further contain at least one selected from the group consisting of Sr, Pb, and Ca in addition to Ba.
  • the strontium ferrite may further contain at least one selected from the group consisting of Ba, Pb, and Ca in addition to Sr.
  • the hexagonal ferrite has an average composition represented by the general formula MFe 12 O 19.
  • M is, for example, at least one metal selected from the group consisting of Ba, Sr, Pb, and Ca, preferably at least one metal selected from the group consisting of Ba and Sr.
  • M may be a combination of Ba and at least one metal selected from the group consisting of Sr, Pb, and Ca.
  • M may also be a combination of Sr and at least one metal selected from the group consisting of Ba, Pb, and Ca.
  • a part of Fe may be substituted with another metal element.
  • the average particle size of the magnetic particles is preferably 13 nm to 20 nm, more preferably 13 nm to 19 nm, even more preferably 13 nm to 18 nm, particularly preferably 14 nm to 17 nm, and most preferably 14 nm to 16 nm.
  • the average particle size of the magnetic particles is 20 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high recording density magnetic tape MT.
  • the average particle size of the magnetic particles is 13 nm or more, the dispersibility of the magnetic particles is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.5 to 2.8, and even more preferably 1.8 to 2.7.
  • the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed.
  • the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.
  • the average particle size and average aspect ratio of the magnetic particles are obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT. Next, the magnetic tape MT to be measured is processed by the FIB method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the TEM image of the cross section described later.
  • the carbon layer is formed by deposition on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side, and the tungsten layer is further formed by deposition or sputtering on the surface on the magnetic layer 43 side.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. In other words, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.
  • the cross section of the obtained thin sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) at an acceleration voltage of 200 kV and a total magnification of 500,000 times in the thickness direction of the magnetic layer 43 so as to include the entire magnetic layer 43, and a TEM image is taken.
  • TEM images are prepared in such a number that 50 particles can be extracted that can measure the plate diameter DB and plate thickness DA (see Figure 7) shown below.
  • the size of the hexagonal ferrite particles (hereinafter referred to as "particle size") is defined as the plate diameter DB, which is the long diameter of the plate surface or bottom surface, when the shape of the particle observed in the above TEM image is plate-like or columnar (however, the thickness or height is smaller than the long diameter of the plate surface or bottom surface) as shown in Figure 7.
  • the thickness or height of the particle observed in the above TEM image is defined as the plate thickness DA.
  • the thickness or height of a particle observed in the TEM image is not constant within a single particle, the thickness or height of the maximum particle is defined as the plate thickness DA.
  • 50 particles are selected from the captured TEM image based on the following criteria. Particles that are partially outside the field of view of the TEM image are not measured, and only particles that have a clear outline and exist in isolation are measured. If there are overlapping particles, those with a clear boundary between them and whose overall shape can be determined are measured as individual particles, but particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.
  • FIG. 8 and 9 show the first and second examples of TEM images, respectively.
  • the particles indicated by the arrows a and d are selected because the plate thickness (thickness or height) DA of the particles can be clearly confirmed.
  • the plate thickness DA of each of the selected 50 particles is measured.
  • the plate thicknesses DA thus obtained are simply averaged (arithmetic average) to obtain the average plate thickness DA ave .
  • the average plate thickness DA ave is the average particle plate thickness.
  • the plate diameter DB of each magnetic particle is measured.
  • 50 particles whose plate diameter DB of the particles can be clearly confirmed are selected from the TEM image taken. For example, in FIG. 8 and FIG.
  • the particles indicated by the arrows b and c are selected because the plate diameter DB of the particles can be clearly confirmed.
  • the plate diameter DB of each of the selected 50 particles is measured.
  • the plate diameter DB thus obtained is simply averaged (arithmetic average) to obtain the average plate diameter DB ave .
  • the average plate diameter DB ave is the average particle size.
  • the average aspect ratio of the particles ( DBave / DAave ) is calculated from the average plate thickness DAave and the average plate diameter DBave .
  • the average particle volume of the magnetic particles is preferably 500 nm3 or more and 2500 nm3 or less, more preferably 500 nm3 or more and 1500 nm3 or less, even more preferably 500 nm3 or more and 1400 nm3 or less, particularly preferably 600 nm3 or more and 1200 nm3 or less, and most preferably 600 nm3 or more and 1000 nm3 or less.
  • the average particle volume of the magnetic particles is 2500 nm3 or less, the same effect as when the average particle size of the magnetic particles is 22 nm or less can be obtained.
  • the average particle volume of the magnetic particles is 500 nm3 or more, the same effect as when the average particle size of the magnetic particles is 13 nm or more can be obtained.
  • the average particle volume of the magnetic particles is calculated as follows. First, the average plate thickness DA ave and the average plate diameter DB ave are calculated as described above in relation to the method for calculating the average particle size of the magnetic particles. Next, the average volume V of the magnetic particles is calculated using the following formula.
  • the ⁇ -iron oxide particles are hard magnetic particles that can obtain high coercivity even in the case of fine particles.
  • the ⁇ -iron oxide particles are spherical or cubic.
  • the term “spherical” includes “approximately spherical”.
  • the term “cubic” includes “approximately cubic”. Since the ⁇ -iron oxide particles have the above-mentioned shape, when the ⁇ -iron oxide particles are used as the magnetic particles, the contact area between the particles in the thickness direction of the magnetic tape MT can be reduced and the aggregation between the particles can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as the magnetic particles. Therefore, the dispersibility of the magnetic particles can be improved, and further excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • SNR electromagnetic conversion characteristics
  • the ⁇ -iron oxide particles may have a composite particle structure. More specifically, the ⁇ -iron oxide particles include an ⁇ -iron oxide portion and a portion having soft magnetism or a portion having a higher saturation magnetization ⁇ s and a smaller coercive force Hc than ⁇ -iron oxide (hereinafter referred to as the "soft magnetic portion, etc.”).
  • the ⁇ -iron oxide portion contains ⁇ -iron oxide.
  • the ⁇ -iron oxide contained in the ⁇ -iron oxide portion preferably has ⁇ -Fe 2 O 3 crystals as a main phase, and more preferably is made of single-phase ⁇ -Fe 2 O 3 .
  • the soft magnetic portion is in contact with at least a portion of the ⁇ -iron oxide portion. Specifically, the soft magnetic portion may partially cover the ⁇ -iron oxide portion, or may cover the entire periphery of the ⁇ -iron oxide portion.
  • the soft magnetic portion (the magnetic portion having a higher saturation magnetization ⁇ s and a smaller coercive force Hc than ⁇ -iron oxide) includes, for example, a soft magnetic material such as ⁇ -Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy.
  • ⁇ -Fe may be obtained by reducing the ⁇ -iron oxide contained in the ⁇ -iron oxide portion.
  • the portion having soft magnetic properties may contain, for example, Fe 3 O 4 , ⁇ -Fe 2 O 3 , or spinel ferrite.
  • the coercive force Hc of the ⁇ -iron oxide portion alone can be kept high to ensure thermal stability, while the coercive force Hc of the ⁇ -iron oxide particle (composite particle) as a whole can be adjusted to a coercive force Hc suitable for recording.
  • the ⁇ iron oxide particles may contain an additive instead of the structure of the composite particles, or may have the structure of the composite particles and contain an additive. In this case, part of the Fe in the ⁇ iron oxide particles is replaced with the additive.
  • the additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one selected from the group consisting of Al, Ga and In, and even more preferably at least one selected from the group consisting of Al and Ga.
  • the ⁇ -iron oxide containing the additive is an ⁇ -Fe2 - xMxO3 crystal (wherein M is a metal element other than iron, preferably a trivalent metal element, more preferably at least one selected from the group consisting of Al, Ga and In, and even more preferably at least one selected from the group consisting of Al and Ga; x is, for example, 0 ⁇ x ⁇ 1).
  • the average particle size of the magnetic particles is preferably 10 nm to 20 nm, more preferably 10 nm to 18 nm, even more preferably 10 nm to 16 nm, particularly preferably 10 nm to 15 nm, and most preferably 10 nm to 14 nm.
  • the area with a size of 1/2 the recording wavelength becomes the actual magnetization area. Therefore, by setting the average particle size of the magnetic particles to half or less of the shortest recording wavelength, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR).
  • the average particle size of the magnetic particles is 20 nm or less, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR) in a high recording density magnetic tape MT (e.g., a magnetic tape MT configured to be able to record signals at the shortest recording wavelength of 40 nm or less).
  • a high recording density magnetic tape MT e.g., a magnetic tape MT configured to be able to record signals at the shortest recording wavelength of 40 nm or less.
  • the average particle size of the magnetic particles is 10 nm or more, the dispersibility of the magnetic particles is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, even more preferably 1.0 to 2.1, and particularly preferably 1.0 to 1.8.
  • the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed.
  • the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.
  • the average particle size and the average aspect ratio of the magnetic particles are obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT. Next, the magnetic tape MT to be measured is processed by the FIB (Focused Ion Beam) method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment for observing the TEM image of the cross section described later.
  • FIB Fluorused Ion Beam
  • the carbon layer is formed by deposition on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side, and the tungsten layer is further formed by deposition or sputtering on the surface on the magnetic layer 43 side.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. In other words, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.
  • the cross section of the obtained thin sample is observed with a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times so that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken.
  • 50 particles whose particle shape can be clearly confirmed are selected from the taken TEM image, and the long axis length DL and short axis length DS of each particle are measured.
  • the long axis length DL means the maximum distance between two parallel lines drawn from all angles so as to be in contact with the contour of each particle (so-called maximum Feret diameter).
  • the short axis length DS means the maximum length of the particle in the direction perpendicular to the long axis (DL) of the particle.
  • the long axis lengths DL of the measured 50 particles are simply averaged (arithmetic average) to obtain the average long axis length DL ave .
  • the average long axis length DL ave thus obtained is the average particle size of the magnetic particles.
  • the minor axis lengths DS of the 50 particles are simply averaged (arithmetic mean) to determine the average minor axis length DSave .
  • the average aspect ratio of the particles ( DLave / DSave ) is then calculated from the average major axis length DLave and the average minor axis length DSave .
  • the average particle volume of the magnetic particles is preferably 500 nm3 or more and 4000 nm3 or less, more preferably 500 nm3 or more and 3000 nm3 or less, even more preferably 500 nm3 or more and 2000 nm3 or less, particularly preferably 600 nm3 or more and 1600 nm3 or less, and most preferably 600 nm3 or more and 1300 nm3 or less. Since the noise of a magnetic tape MT is generally inversely proportional to the square root of the number of particles (i.e., proportional to the square root of the particle volume), by making the particle volume smaller, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR).
  • SNR electromagnetic conversion characteristics
  • the average particle volume of the magnetic particles is 4000 nm3 or less, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR) in the same way as when the average particle size of the magnetic particles is 20 nm or less.
  • the average particle volume of the magnetic particles is 500 nm3 or more, it is possible to obtain the same effect as when the average particle size of the magnetic particles is 10 nm or more.
  • the average volume of the magnetic particles is found as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT. Next, the cut magnetic tape MT is processed by the FIB (Focused Ion Beam) method or the like to be thinned. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the TEM image of the cross section described later.
  • FIB Fluorused Ion Beam
  • the carbon film is formed by deposition on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side, and the tungsten thin film is further formed by deposition or sputtering on the surface on the magnetic layer 43 side.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. In other words, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.
  • the obtained thin sample is observed in cross section in the thickness direction of the magnetic layer 43 at an acceleration voltage of 200 kV and a total magnification of 500,000 times to include the entire magnetic layer 43, and a TEM image is obtained.
  • the magnification and acceleration voltage may be adjusted appropriately depending on the type of device.
  • 50 particles whose particle shapes are clear are selected from the TEM image taken, and the side length DC of each particle is measured.
  • the side lengths DC of the 50 particles measured are simply averaged (arithmetic average) to obtain the average side length DC ave .
  • the average volume V ave (particle volume) of the magnetic particles is calculated from the following formula using the average side length DC ave .
  • V ave DC ave 3
  • the cobalt ferrite particles preferably have uniaxial crystal anisotropy.
  • the cobalt ferrite particles have uniaxial crystal anisotropy, so that the magnetic particles can be preferentially crystal oriented in the perpendicular direction of the magnetic tape MT.
  • the cobalt ferrite particles have, for example, a cubic shape. In this specification, the cubic shape includes an almost cubic shape.
  • the Co-containing spinel ferrite may further contain at least one selected from the group consisting of Ni, Mn, Al, Cu and Zn in addition to Co.
  • the Co-containing spinel ferrite has, for example, an average composition represented by the following formula.
  • Co x M y Fe 2 O Z (In the formula, M is at least one metal selected from the group consisting of, for example, Ni, Mn, Al, Cu, and Zn.
  • x is a value within the range of 0.4 ⁇ x ⁇ 1.0.
  • y is a value within the range of 0 ⁇ y ⁇ 0.3. However, x and y satisfy the relationship of (x+y) ⁇ 1.0.
  • z is a value within the range of 3 ⁇ z ⁇ 4. A part of Fe may be substituted with another metal element.
  • the average particle size of the magnetic particles is preferably 8 nm or more and 16 nm or less, more preferably 8 nm or more and 13 nm or less, and even more preferably 8 nm or more and 10 nm or less.
  • the average particle size of the magnetic particles is 16 nm or less, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR) in a high recording density magnetic tape MT.
  • the average particle size of the magnetic particles is 8 nm or more, the dispersibility of the magnetic particles is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • the method of calculating the average particle size of the magnetic particles is the same as the method of calculating the average particle size of the magnetic particles when the magnetic particles are ⁇ iron oxide particles.
  • the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, and even more preferably 1.0 to 2.0.
  • the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed.
  • the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.
  • the method of calculating the average aspect ratio of the magnetic particles is the same as the method of calculating the average aspect ratio of the magnetic particles when the magnetic particles are ⁇ iron oxide particle powder.
  • the average particle volume of the magnetic particles is preferably 500 nm3 or more and 4000 nm3 or less, more preferably 600 nm3 or more and 2000 nm3 or less, and even more preferably 600 nm3 or more and 1000 nm3 or less.
  • the average particle volume of the magnetic particles is 4000 nm3 or less, the same effect as when the average particle size of the magnetic particles is 16 nm or less can be obtained.
  • the average particle volume of the magnetic particles is 500 nm3 or more, the same effect as when the average particle size of the magnetic particles is 8 nm or more can be obtained.
  • the method of calculating the average particle volume of the magnetic portion is the same as the method of calculating the average particle volume when the ⁇ iron oxide particles have a cubic shape.
  • the binder includes, for example, a thermoplastic resin.
  • the binder may further include a thermosetting resin or a reactive resin.
  • the thermoplastic resin includes a first thermoplastic resin (first binder) containing chlorine atoms and a second thermoplastic resin (second binder) containing nitrogen atoms. More specifically, the thermoplastic resin includes vinyl chloride resin and urethane resin.
  • vinyl chloride resin means a polymer containing a structural unit derived from vinyl chloride. More specifically, for example, vinyl chloride resin means a homopolymer of vinyl chloride, a polymer of vinyl chloride and a comonomer copolymerizable therewith, and a mixture of these polymers.
  • the vinyl chloride resin includes, for example, at least one selected from the group consisting of vinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, and methacrylate-vinyl chloride copolymer.
  • a urethane-based resin means a resin that contains a urethane bond in at least a part of the molecular chain that constitutes the resin, and may be a urethane resin or a copolymer that contains a urethane bond in a part of the molecular chain.
  • the urethane-based resin may be, for example, one obtained by reacting a polyisocyanate with a polyol.
  • the urethane-based resin may be, for example, one obtained by reacting a polyester with a polyol.
  • the urethane-based resin also includes one obtained by reacting with a curing agent.
  • the polyisocyanate includes at least one selected from the group consisting of, for example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).
  • MDI diphenylmethane diisocyanate
  • TDI tolylene diisocyanate
  • XDI xylylene diisocyanate
  • PDI 1,5-pentamethylene diisocyanate
  • HDI hexamethylene diisocyanate
  • IPDI isophorone diisocyanate
  • polyisocyanate means a compound having two or more isocyanate groups in the molecule.
  • the polyisocyanate may be the polyisocyanate contained in the curing agent.
  • the polyol includes at least one selected from the group consisting of, for example, polyols (diols) having two OH groups, polyols (triols) having three OH groups, polyols (tetraols) having four OH groups, polyols (pentaols) having five OH groups, and polyols (hexaols) having six OH groups.
  • the polyol includes at least one selected from the group consisting of, for example, polyester-based polyols, polyether-based polyols, polycarbonate-based polyols, polyesteramide-based polyols, and acrylate-based polyols.
  • the polyester includes, for example, at least one selected from the group consisting of phthalic acid-based polyesters and aliphatic polyesters.
  • the thermoplastic resin may further include a thermoplastic resin other than vinyl chloride resin and urethane resin.
  • a thermoplastic resin may include at least one selected from the group consisting of, for example, vinyl acetate, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene butadiene copolymer, polyester resin, amino resin, and synthetic rubber.
  • Thermosetting resin includes at least one selected from the group consisting of, for example, phenolic resin, epoxy resin, polyurethane curing resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, and urea formaldehyde resin.
  • all of the above-mentioned binders may contain polar functional groups such as -SO 3 M, -OSO 3 M, -COOM, P ⁇ O(OM) 2 (wherein M represents a hydrogen atom or an alkali metal such as lithium, potassium or sodium), side chain amines having terminal groups represented by -NR1R2 or -NR1R2R3 + X- , main chain amines represented by >NR1R2 + X- (wherein R1, R2 and R3 represent a hydrogen atom or a hydrocarbon group, and X- represents a halogen element ion such as fluorine, chlorine, bromine or iodine, an inorganic ion or an organic ion), -OH, -SH, -CN and epoxy groups.
  • the amount of these polar functional groups introduced into the binder is preferably 10 -1 or more and 10 -8 mol/g or less, and more preferably 10 -2 or more and 10
  • Some of the conductive particles contained in the magnetic layer 43 may protrude from the magnetic surface to form a plurality of protrusions 430.
  • the electrical resistance of the magnetic surface can be reduced, and charging of the magnetic surface can be suppressed.
  • dynamic friction between the head unit 56 and the magnetic surface during running of the magnetic tape MT can be reduced.
  • the conductive particles are preferably an antistatic agent and a solid lubricant.
  • the conductive particles are preferably particles containing carbon.
  • As the carbon-containing particles for example, at least one type selected from the group consisting of carbon particles and hybrid particles can be used, and carbon particles are preferably used.
  • the average primary particle size of the conductive particles is preferably 100 nm or less. When the average primary particle size of the conductive particles is 100 nm or less, even when the conductive particles are particles with a large particle size distribution (e.g., carbon black, etc.), the inclusion of particles that are excessively large relative to the thickness of the magnetic layer 43 is suppressed.
  • carbon particles for example, one or more selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene can be used, and among these carbon particles, it is preferable to use carbon black.
  • carbon black for example, Seast TA manufactured by Tokai Carbon Co., Ltd., Asahi #15, #15HS, etc. manufactured by Asahi Carbon Co., Ltd. can be used.
  • the hybrid particles include carbon and a material other than carbon.
  • the material other than carbon is, for example, an organic material or an inorganic material.
  • the hybrid particles may be hybrid particles in which carbon is attached to the surface of an inorganic particle.
  • the hybrid particles may be hybrid carbon in which carbon is attached to the surface of a silica particle.
  • Some of the abrasive particles contained in the magnetic layer 43 may protrude from the magnetic surface to form a plurality of protrusions 430. When the head unit 56 slides over the magnetic tape MT, the protrusions 430 formed by the abrasive particles can come into contact with the head unit 56.
  • the lower limit of the Mohs hardness of the abrasive particles is preferably 7.0 or more, more preferably 7.5 or more, even more preferably 8.0 or more, and particularly preferably 8.5 or more, from the viewpoint of suppressing deformation due to contact with the head unit 56.
  • the upper limit of the Mohs hardness of the abrasive particles is preferably 9.5 or less, from the viewpoint of suppressing wear of the head unit 56.
  • the abrasive particles are preferably inorganic particles.
  • inorganic particles include ⁇ -alumina with an ⁇ conversion rate of 90% or more, ⁇ -alumina, ⁇ -alumina, silicon carbide, chromium oxide, cerium oxide, ⁇ -iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, acicular ⁇ -iron oxide obtained by dehydrating and annealing magnetic iron oxide raw materials, and those surface-treated with aluminum and/or silica as necessary, diamond powder, etc.
  • alumina particles such as ⁇ -alumina, ⁇ -alumina, and ⁇ -alumina, and silicon carbide are preferably used.
  • the abrasive particles may be in any shape such as needle-shaped, spherical, or cube-shaped, but those with some corners in the shape are preferred because they have high abrasiveness.
  • the lubricant contains at least one selected from, for example, fatty acids and fatty acid esters, preferably both fatty acids and fatty acid esters.
  • the inclusion of a lubricant in the magnetic layer 43 contributes to improving the running stability of the magnetic tape MT. More particularly, the magnetic layer 43 contains a lubricant and has pores, thereby achieving good running stability. The improvement in running stability is believed to be due to the lubricant adjusting the dynamic friction coefficient of the magnetic layer 43 side surface of the magnetic tape MT to a value suitable for running the magnetic tape MT.
  • the fatty acid may preferably be a compound represented by the following general formula (1) or (2).
  • the fatty acid may contain either a compound represented by the following general formula (1) or a compound represented by the following general formula (2), or may contain both.
  • the fatty acid ester may preferably be a compound represented by the following general formula (3), (4) or (5).
  • the fatty acid ester may contain one, two or three of the compounds represented by the following general formula (3), (4) and (5).
  • the lubricant contains either one or both of the compounds represented by general formula (1) and general formula (2), and one, two or three of the compounds represented by general formula (3), (4) and (5), thereby making it possible to suppress an increase in the dynamic friction coefficient due to repeated recording or playback of the magnetic tape MT.
  • k is an integer selected from the range of 14 or more and 22 or less, more preferably from the range of 14 or more and 18 or less.
  • the antistatic agent includes carbon particles.
  • the antistatic agent may further include at least one selected from the group consisting of a natural surfactant, a nonionic surfactant, a cationic surfactant, etc.
  • the carbon particles include at least one selected from the group consisting of, for example, carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.
  • the curing agent includes, for example, polyisocyanate.
  • the polyisocyanate may include, for example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), or the like as an isocyanate source.
  • the polyisocyanate may have a TMP adduct structure, an isocyanurate structure, a biuret structure, or an allophanate structure.
  • polyisocyanates include aromatic polyisocyanates such as an adduct of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as an adduct of hexamethylene diisocyanate (HMDI) and an active hydrogen compound.
  • TDI tolylene diisocyanate
  • HMDI hexamethylene diisocyanate
  • the weight average molecular weight of these polyisocyanates is preferably in the range of 100 to 3,000.
  • anti-rust examples include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.
  • Non-magnetic reinforcing particles examples include aluminum oxide ( ⁇ , ⁇ or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutile or anatase type titanium oxide), and the like.
  • the underlayer 42 is intended to reduce the unevenness of the surface of the substrate 41 and adjust the unevenness of the magnetic surface.
  • the underlayer 42 is a non-magnetic layer containing non-magnetic particles, a binder, and a lubricant.
  • the underlayer 42 supplies the lubricant to the magnetic surface.
  • the underlayer 42 may further contain at least one additive selected from the group consisting of an antistatic agent, a hardener, an anti-rust agent, etc., as necessary.
  • the average thickness t2 of the underlayer 42 is preferably 0.30 ⁇ m or more and 1.20 ⁇ m or less, more preferably 0.30 ⁇ m or more and 0.90 ⁇ m or less, and even more preferably 0.30 ⁇ m or more and 0.60 ⁇ m or less.
  • the average thickness t2 of the underlayer 42 is determined in the same manner as the average thickness t1 of the magnetic layer 43. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the underlayer 42.
  • the average thickness t2 of the underlayer 42 is 1.20 ⁇ m or less, the elasticity of the magnetic tape MT due to an external force is further increased, and therefore, the adjustment of the width of the magnetic tape MT by adjusting the tension becomes even easier.
  • the underlayer 42 preferably has a plurality of holes. By storing lubricant in these holes, it is possible to further suppress the decrease in the amount of lubricant supplied between the magnetic surface and the head unit 56 even after repeated recording or playback (i.e., even after the head unit 56 is in contact with the surface of the magnetic tape MT and the tape is repeatedly run). This makes it possible to further suppress the increase in the dynamic friction coefficient. In other words, it is possible to obtain even better running stability.
  • the non-magnetic particles include at least one of inorganic particles and organic particles.
  • the non-magnetic particles may be carbon particles such as carbon black.
  • One type of non-magnetic particles may be used alone, or two or more types of non-magnetic particles may be used in combination.
  • the inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides.
  • the shapes of the non-magnetic particles include, for example, various shapes such as needles, spheres, cubes, and plates, but are not limited to these shapes.
  • Binding agent, lubricant The binder and lubricant are the same as those in the magnetic layer 43 described above.
  • the antistatic agent, hardener and rust inhibitor are the same as those in the magnetic layer 43 described above.
  • the back layer 44 contains a binder and non-magnetic particles.
  • the back layer 44 may further contain at least one additive selected from the group consisting of a lubricant, a hardener, an antistatic agent, etc., as necessary.
  • the binder and non-magnetic particles are the same as those in the underlayer 42 described above.
  • the hardener and antistatic agent are the same as those in the magnetic layer 43 described above.
  • the average particle size of the non-magnetic particles is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less.
  • the average particle size of the non-magnetic particles is determined in the same manner as the average particle size of the magnetic particles described above.
  • the non-magnetic particles may include non-magnetic particles having two or more particle size distributions.
  • the upper limit of the average thickness of the back layer 44 is preferably 0.60 ⁇ m or less. If the upper limit of the average thickness of the back layer 44 is 0.60 ⁇ m or less, the thickness of the underlayer 42 and the base 41 can be kept thick even if the average thickness of the magnetic tape MT is 5.30 ⁇ m or less, so that the running stability of the magnetic tape MT within a recording and reproducing device can be maintained.
  • the lower limit of the average thickness of the back layer 44 is not particularly limited, but is, for example, 0.20 ⁇ m or more.
  • the average thickness t b of the back layer 44 is obtained as follows. First, the average thickness t T of the magnetic tape MT is measured. The method for measuring the average thickness t T is as described in the "Average Thickness of Magnetic Tape" below. Next, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 250 mm at a position 30 to 40 m from one end of the outer periphery of the magnetic tape MT in the longitudinal direction to prepare a sample. Next, the back layer 44 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • MEK methyl ethyl ketone
  • the thickness of the sample is measured at five positions using a Mitutoyo laser hologram (LGH-110C), and the measured values are simply averaged (arithmetic average) to calculate the average value t B [ ⁇ m]. Then, the average thickness t b [ ⁇ m] of the back layer 44 is obtained from the following formula.
  • the upper limit of the average thickness (average total thickness) tT of the magnetic tape MT is preferably 5.30 ⁇ m or less, more preferably 5.10 ⁇ m or less, even more preferably 4.90 ⁇ m or less, and particularly preferably 4.70 ⁇ m or less.
  • the lower limit of the average thickness tT of the magnetic tape MT is not particularly limited, but is, for example, 3.50 ⁇ m or more.
  • the average thickness tT of the magnetic tape MT is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 250 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT to prepare a sample. Next, the thickness of the sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the measured values are simply averaged (arithmetic average) to calculate the average thickness tT [ ⁇ m]. The five measurement positions are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.
  • LGH-110C Mitutoyo Laser Hologram
  • the upper limit of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 2000 Oe or less, more preferably 1900 Oe or less, and even more preferably 1800 Oe or less. If the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 2000 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording density.
  • the lower limit of the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is preferably 1000 Oe or more. If the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000 Oe or more, demagnetization due to leakage flux from the recording head can be suppressed.
  • the coercive force Hc2 is obtained as follows. First, the magnetic tape MT contained in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position between 30 m and 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT. Three pieces are stacked with double-sided tape so that the longitudinal direction of the magnetic tape MT is the same, and then punched out with a ⁇ 6.39 mm punch to prepare a measurement sample. At this time, marking is performed with any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be identified.
  • the M-H loop of the measurement sample (whole magnetic tape MT) corresponding to the longitudinal direction (running direction) of the magnetic tape MT is measured using a vibrating sample magnetometer (VSM).
  • VSM vibrating sample magnetometer
  • the coating film (undercoat layer 42, magnetic layer 43, back layer 44, etc.) of the magnetic tape MT cut out above is wiped off with acetone, ethanol, etc., leaving only the substrate 41.
  • Three of the obtained substrates 41 are then stacked together with double-sided tape, and punched out with a ⁇ 6.39 mm punch to create a sample for background correction (hereinafter simply referred to as the "correction sample").
  • the M-H loop of the correction sample (substrate 41) corresponding to the longitudinal direction of substrate 41 (the longitudinal direction of magnetic tape MT) is measured using a VSM.
  • a high-sensitivity vibration sample magnetometer "VSM-P7-15 type" manufactured by Toei Industry Co., Ltd. is used.
  • the measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, number of MH averages: 20.
  • background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (entire magnetic tape MT), and the M-H loop after background correction is obtained.
  • the measurement and analysis program included with the "VSM-P7-15" is used for this background correction calculation.
  • the coercive force Hc2 is obtained from the obtained M-H loop after background correction. Note that the measurement and analysis program included with the "VSM-P7-15" is used for this calculation.
  • the squareness ratio S1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 62% or more, more preferably 65% or more, even more preferably 68% or more, particularly preferably 72% or more, and most preferably 75% or more.
  • the squareness ratio S1 is 62% or more, the perpendicular orientation of the magnetic particles is sufficiently high, so that further excellent electromagnetic conversion characteristics can be obtained.
  • the squareness ratio S1 in the vertical direction of the magnetic tape MT is obtained as follows. First, the magnetic tape MT contained in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT. Three pieces are stacked with double-sided tape so that the longitudinal direction of the magnetic tape MT is the same, and then punched out with a ⁇ 6.39 mm punch to prepare a measurement sample. At this time, marking is performed with any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be identified.
  • the M-H loop of the measurement sample (whole magnetic tape MT) corresponding to the vertical direction of the magnetic tape MT (vertical direction of the magnetic tape MT) is measured using a vibrating sample magnetometer (VSM).
  • VSM vibrating sample magnetometer
  • the coating film (undercoat layer 42, magnetic layer 43, back layer 44, etc.) of the magnetic tape MT cut out above is wiped off with acetone, ethanol, etc., leaving only the substrate 41.
  • Three of the obtained substrates 41 are then stacked together with double-sided tape, and punched out with a ⁇ 6.39 mm punch to create a sample for background correction (hereinafter simply referred to as the "correction sample").
  • the M-H loop of the correction sample (substrate 41) corresponding to the perpendicular direction of substrate 41 (perpendicular direction of magnetic tape MT) is measured using a VSM.
  • a high-sensitivity vibration sample magnetometer "VSM-P7-15 type" manufactured by Toei Industry Co., Ltd. is used.
  • the measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, number of MH averages: 20.
  • background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (entire magnetic tape MT), to obtain the M-H loop after background correction.
  • the measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction.
  • the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, and most preferably 15% or less. If the squareness ratio S2 is 35% or less, the vertical orientation of the magnetic particles is sufficiently high, and therefore even better electromagnetic conversion characteristics can be obtained.
  • One of the squareness ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT may be within the above preferred range, and the other may be outside the above preferred range.
  • both the squareness ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT may be within the above preferred range.
  • the squareness ratio S2 in the longitudinal direction of the magnetic tape MT is determined in the same manner as the squareness ratio S1, except that the M-H loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the substrate 41.
  • the ratio Hc2/Hc1 of the coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT to the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT preferably satisfies the relationship Hc2/Hc1 ⁇ 0.8, more preferably Hc2/Hc1 ⁇ 0.75, even more preferably Hc2/Hc1 ⁇ 0.7, particularly preferably Hc2/Hc1 ⁇ 0.65, and most preferably Hc2/Hc1 ⁇ 0.6.
  • the magnetization transition width can be reduced and a high-output signal can be obtained during signal reproduction, so that even better electromagnetic conversion characteristics can be obtained.
  • Hc2 when Hc2 is small, the magnetization reacts sensitively to the perpendicular magnetic field from the recording head, so that a good recording pattern can be formed.
  • the ratio Hc2/Hc1 is Hc2/Hc1 ⁇ 0.8
  • it is particularly effective that the average thickness t1 of the magnetic layer 43 is 90 nm or less. If the average thickness t1 of the magnetic layer 43 exceeds 90 nm, when a ring-type head is used as a recording head, the lower region of the magnetic layer 43 (the region on the underlayer 42 side) is magnetized in the longitudinal direction of the magnetic tape MT, and the magnetic layer 43 may not be uniformly magnetized in the thickness direction. Therefore, even if the ratio Hc2/Hc1 is Hc2/Hc1 ⁇ 0.8 (i.e., even if the degree of perpendicular orientation of the magnetic particles is increased), there is a risk that further excellent electromagnetic conversion characteristics cannot be obtained.
  • Hc2/Hc1 is not particularly limited, but for example, 0.5 ⁇ Hc2/Hc1.
  • Hc2/Hc1 represents the degree of vertical orientation of the magnetic particles, and the smaller Hc2/Hc1 is, the higher the degree of vertical orientation of the magnetic particles.
  • the method for calculating the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is as described above.
  • the coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is calculated in the same manner as the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT, except that the M-H loop is measured in the perpendicular direction (thickness direction) of the magnetic tape MT and the substrate 41.
  • the activation volume Vact is preferably 8000 nm3 or less, more preferably 6000 nm3 or less, even more preferably 5000 nm3 or less, particularly preferably 4000 nm3 or less, and most preferably 3000 nm3 or less.
  • the activation volume Vact is 8000 nm3 or less, the dispersion state of the magnetic particles is good, so that the bit inversion region can be made steep, and the deterioration of the magnetization signal recorded on the adjacent track due to the leakage magnetic field from the recording head can be suppressed. Therefore, there is a risk that further excellent electromagnetic conversion characteristics cannot be obtained.
  • V act is calculated by the following formula derived by Street & Woolley.
  • Vact ( nm3 ) kB ⁇ T ⁇ Xirr /( ⁇ 0 ⁇ Ms ⁇ S) (wherein k B is Boltzmann's constant (1.38 ⁇ 10 ⁇ 23 J/K), T is temperature (K), X irr is irreversible magnetic susceptibility, ⁇ 0 is vacuum permeability, S is magnetic viscosity coefficient, and Ms is saturation magnetization (emu/cm 3 )).
  • the irreversible magnetic susceptibility X irr , saturation magnetization Ms, and magnetic viscosity coefficient S substituted into the above formula are determined using a VSM as follows.
  • the measurement direction using the VSM is the perpendicular direction (thickness direction) of the magnetic tape MT.
  • the measurement using the VSM is performed on a measurement sample cut out from a long magnetic tape MT at 25°C ⁇ 2°C and 50% RH ⁇ 5% RH.
  • no "demagnetization correction" is performed.
  • the irreversible magnetic susceptibility ⁇ irr is defined as the slope of the residual magnetization curve (DCD curve) near the residual coercivity Hr.
  • DCD curve residual magnetization curve
  • Magnetic viscosity coefficient S First, a magnetic field of -1193 kA/m (15 kOe) is applied to the entire magnetic tape MT (measurement sample), and the magnetic field is returned to zero to create a residual magnetization state. After that, a magnetic field equivalent to the value of the residual coercivity Hr obtained from the DCD curve is applied in the opposite direction. With the magnetic field applied, the amount of magnetization is continuously measured at regular time intervals for 1000 seconds. The magnetic viscosity coefficient S is calculated by referring to the relationship between time t and amount of magnetization M(t) obtained in this way in the following formula.
  • M(t) M0+S ⁇ ln(t) (where M(t) is the amount of magnetization at time t, M0 is the initial amount of magnetization, S is the magnetic viscosity coefficient, and ln(t) is the natural logarithm of time.)
  • the surface roughness Rb of the back surface (surface roughness of the back layer 44) satisfies Rb ⁇ 6.0 [nm].
  • Rb surface roughness of the back layer 44
  • the surface roughness Rb of the back surface is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 100 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT to prepare a sample. Next, the sample is placed on a slide glass so that the surface to be measured (the surface on the magnetic layer 43 side) faces up, and the end of the sample is fixed with mending tape. The surface shape is measured using a VertScan (20x objective lens) as a measuring device, and the surface roughness Rb of the back surface is obtained from the following formula based on the ISO 25178 standard. The measurement conditions are as follows.
  • Non-contact roughness meter using optical interference (Ryoka Systems Co., Ltd. non-contact surface and layer cross-sectional shape measurement system VertScan R5500GL-M100-AC)
  • Objective lens 20x Measurement area: 640 x 480 pixels (field of view: approx.
  • Measurement mode phase Wavelength filter: 520 nm
  • CCD 1/3 inch
  • Noise reduction filter Smoothing 3x3
  • Surface correction Correction using quadratic polynomial approximation surface
  • Measurement software VS-Measure Version 5.5.2
  • Analysis software VS-viewer Version 5.5.5 After measuring the surface roughness at five points in the longitudinal direction of the magnetic tape MT as described above, the average value of the arithmetic mean roughness S a (nm) automatically calculated from the surface profile obtained at each position is defined as the surface roughness R b (nm) of the back surface.
  • the upper limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less.
  • the Young's modulus in the longitudinal direction of the magnetic tape MT is 9.0 GPa or less, the elasticity of the magnetic tape MT due to external forces is further increased, so that the adjustment of the width of the magnetic tape MT by tension adjustment becomes even easier. Therefore, off-track can be further appropriately suppressed, and data recorded on the magnetic tape MT can be reproduced more accurately.
  • the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more.
  • the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, the decrease in running stability can be suppressed.
  • the Young's modulus of the magnetic tape MT in the longitudinal direction is a value that indicates the resistance of the magnetic tape MT to expansion and contraction in the longitudinal direction due to external forces; the larger this value, the more difficult it is for the magnetic tape MT to expand and contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT can expand and contract in the longitudinal direction due to external forces.
  • the Young's modulus in the longitudinal direction of the magnetic tape MT is a value related to the longitudinal direction of the magnetic tape MT, it also correlates with the difficulty of the magnetic tape MT to expand and contract in the width direction. In other words, the larger this value is, the more difficult it is for the magnetic tape MT to expand and contract in the width direction due to external forces, and the smaller this value is, the more easily the magnetic tape MT will expand and contract in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the magnetic tape MT to be small as described above, 9.0 GPa or less.
  • a tensile tester (AG-100D, manufactured by Shimadzu Corporation) is used to measure the Young's modulus in the tape longitudinal direction.
  • the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut to a length of 180 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT to prepare a measurement sample.
  • a jig capable of fixing the tape width (1/2 inch) is attached to the tensile tester, and the top and bottom of the tape width are fixed. The distance (length of the tape between the chucks) is set to 100 mm.
  • the Young's modulus is calculated using the following formula.
  • E(N/ m2 ) (( ⁇ N/S)/( ⁇ x/L)) ⁇ 106 ⁇ N: Change in stress (N)
  • S Cross-sectional area of the test piece (mm 2 )
  • ⁇ x Elongation (mm)
  • L Distance between gripping jigs (mm)
  • the cross-sectional area S of the measurement sample 10S is the cross-sectional area before the tensile operation, and is calculated by multiplying the width (1/2 inch) of the measurement sample 10S by the thickness of the measurement sample 10S.
  • the range of tensile stress when performing the measurement is set to a linear region tensile stress range depending on the thickness of the magnetic tape MT, etc.
  • the stress range is set to 0.2 N to 0.7 N, and the stress change ( ⁇ N) and elongation ( ⁇ x) at this time are used for calculation.
  • the Young's modulus is measured at 25° C. ⁇ 2° C. and 50% RH ⁇ 5% RH.
  • the Young's modulus in the longitudinal direction of the substrate 41 is preferably 7.8 GPa or less, more preferably 7.0 GPa or less, even more preferably 6.6 GPa or less, and particularly preferably 6.4 GPa or less.
  • the Young's modulus in the longitudinal direction of the substrate 41 is 7.8 GPa or less, the elasticity of the magnetic tape MT due to external force is further increased, so that the adjustment of the width of the magnetic tape MT by tension adjustment becomes easier. Therefore, off-track can be further appropriately suppressed, and data recorded on the magnetic tape MT can be reproduced more accurately.
  • the lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is preferably 2.5 GPa or more, more preferably 3.0 GPa or more.
  • the lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is 2.5 GPa or more, the decrease in running stability can be suppressed.
  • the Young's modulus in the longitudinal direction of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out to a length of 180 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT. Next, the underlayer 42, magnetic layer 43, and back layer 44 are removed from the cut magnetic tape MT to obtain the substrate 41. Using this substrate 41, the Young's modulus in the longitudinal direction of the substrate 41 is determined in the same manner as for the Young's modulus in the longitudinal direction of the magnetic tape MT.
  • the thickness of the base 41 accounts for more than half of the total thickness of the magnetic tape MT. Therefore, the Young's modulus in the longitudinal direction of the base 41 correlates with the resistance of the magnetic tape MT to expansion and contraction due to external forces; the larger this value, the less likely the magnetic tape MT is to expand and contract in the width direction due to external forces, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external forces.
  • the Young's modulus in the longitudinal direction of the substrate 41 is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the difficulty of the magnetic tape MT to expand and contract in the width direction. In other words, the larger this value is, the more difficult it is for the magnetic tape MT to expand and contract in the width direction due to external forces, and the smaller this value is, the more easily the magnetic tape MT will expand and contract in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the substrate 41 to be small as described above, 7.8 GPa or less.
  • the ratio I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 of the average value I ⁇ n ⁇ 5 of the integrated value of PSD in the range of spatial wavelength ⁇ n ⁇ 5 ⁇ m to the average value I 10 ⁇ n ⁇ 20 of the integrated value of PSD in the range of 10 ⁇ m ⁇ spatial wavelength ⁇ n ⁇ 20 ⁇ m is 3.00 or less, preferably 2.80 or less, more preferably 2.60 or less, 2.40 or less, 2.20 or
  • the ratio I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 exceeds 3.00, the components of short wavelength ⁇ ( ⁇ 5 ⁇ m) become more numerous than the components of long wavelength ⁇ (0 ⁇ m ⁇ 20 ⁇ m) in the surface irregularities on the magnetic layer 43 side, and the distance (hereinafter referred to as "spacing") between the magnetic tape MT and the head unit 56 becomes wider. Therefore, the electromagnetic conversion characteristics deteriorate.
  • the ratio I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut to a length of about 10 cm from a position about 20 m from one end of the magnetic tape MT on the outermost periphery side to obtain sample 1. The magnetic tape MT is also cut to a length of about 10 cm from a position about 50 m from the other end of the magnetic tape MT on the innermost periphery side to obtain sample 2. Next, sample 1 is cut to a size that fits the sample holder and attached to the sample holder, and the magnetic surface of sample 1 is observed with an AFM at three points randomly selected from sample 1 to obtain three two-dimensional surface profile images.
  • the AFM measurement conditions are as follows. Measuring instrument: Medium-sized probe microscope system AFM5500M (manufactured by Hitachi High-Technologies Corporation) Measurement range: 100 ⁇ m x 100 ⁇ m Resolution: X direction 512 x Y direction 512 Measurement mode: DFM (shape) Cantilever: SI-DF40P2 Automatic tilt correction: 1st order Automatic tilt correction: 3rd order
  • the AFM flattening settings were as follows: Calculation target: Off Mask: Off Tilt correction: Off Line Arrangement: Off Calculation direction: XY
  • three two-dimensional surface profile images are obtained from sample 2 using the same procedure as for obtaining three two-dimensional surface profile images from sample 1. In this way, a total of six two-dimensional surface profile images are obtained.
  • an average X-PSD profile of the two-dimensional surface profile image is obtained using image analysis software (Image Metrology, Inc., SPIP (registered trademark) version 6.7.3) in the following manner.
  • image analysis software Image Metrology, Inc., SPIP (registered trademark) version 6.7.3
  • image analysis software Open the two-dimensional surface profile image to be analyzed.
  • Select 2D FFT/PSD analysis from the analysis tab of the image analysis software display the 2D FFT/PSD analysis menu, select average X-PSD profile from the displayed menu, and execute average X-PSD analysis of the two-dimensional surface profile image. This allows the average X-PSD value of the two-dimensional surface profile image to be obtained.
  • PSD [nm 2 ] (average X-PSD value) x 2 x minimum wave number (1.00 x 10 -5 )
  • the minimum wave number (1.00 ⁇ 10 ⁇ 5 ) represents the minimum wave number corresponding to the unevenness of the surface on the magnetic layer 43 side.
  • Fig. 11 shows an example of the PSD calculated by the above process.
  • an integrated value I1 of the PSD [ nm2 ] in the range of spatial wavelength ⁇ n ⁇ 5 ⁇ m, an integrated value I2 of the PSD [ nm2 ] in the range of spatial wavelength ⁇ n ⁇ 10 ⁇ m, and an integrated value I3 of the PSD [ nm2 ] in the range of spatial wavelength ⁇ n ⁇ 20 ⁇ m are calculated.
  • the PSD at each position of spatial wavelength ⁇ n 100/n[ ⁇ m] (where n is an integer between 1 and 255 ) is used to calculate the integrated value I1 , the integrated value I2, and the integrated value I3.
  • the six integrated values I1 calculated from the six two-dimensional surface profile images are simply averaged (arithmetic mean) to calculate the average value I ⁇ n ⁇ 5 of the integrated values I1 .
  • the six integrated values I2 calculated from the six two-dimensional surface profile images are simply averaged (arithmetic mean) to calculate the average value I ⁇ n ⁇ 10 of the integrated values I2 .
  • the six integrated values I3 calculated from the six two-dimensional surface profile images are simply averaged (arithmetic mean) to calculate the average value I ⁇ n ⁇ 20 of the integrated values I3 .
  • the average value I ⁇ n ⁇ 10 is subtracted from the average value I ⁇ n ⁇ 20 to calculate the average value I 10 ⁇ n ⁇ 20 (I ⁇ n ⁇ 20 -I ⁇ n ⁇ 10 ).
  • the ratio of the average value I ⁇ n ⁇ 5 to the average value I 10 ⁇ n ⁇ 20 is calculated.
  • the average value I ⁇ n ⁇ 5 of the integrated value of PSD in the range of spatial wavelength ⁇ n ⁇ 5 ⁇ m obtained by measuring the surface on the magnetic layer 43 side with an AFM is preferably 2.20 nm2 or less, more preferably 2.00 nm2 or less, and even more preferably 1.80 nm2 or less, 1.60 nm2 or less, or 1.40 nm2 or less.
  • the average value I ⁇ n ⁇ 5 of the integrated value is 2.20 nm2 or less, the increase of the component of short wavelength ⁇ ( ⁇ 5 ⁇ m) is suppressed in the unevenness of the surface on the magnetic layer 43 side, and the spacing becomes narrower. Therefore, the electromagnetic conversion characteristics are improved.
  • the average value I10 ⁇ n ⁇ 20 of the integrated values of PSD in the range of 10 ⁇ m ⁇ spatial wavelength ⁇ n ⁇ 20 ⁇ m obtained by measuring the surface on the magnetic layer 43 side with an AFM is preferably 0.65 nm2 or more, more preferably 0.66 nm2 or more, and even more preferably 0.67 nm2 or more. If the average value I10 ⁇ n ⁇ 20 is 0.65 nm2 or more, the contact state between the magnetic tape MT and the head unit 56 is stable, powder falling is reduced, and deterioration of the running properties of the magnetic tape MT is suppressed.
  • the average integrated value I10 ⁇ n ⁇ 20 of the PSD in the range of 10 ⁇ m ⁇ spatial wavelength ⁇ n ⁇ 20 ⁇ m, obtained by measuring the surface on the magnetic layer 43 side with an AFM, is preferably 0.72 nm2 or less, more preferably 0.71 nm2 or less, and even more preferably 0.70 nm2 or less.
  • the average integrated value I10 ⁇ n ⁇ 20 is 0.70 nm2 or less, the spacing between the head unit 56 and the magnetic tape MT can be suppressed, and the electromagnetic conversion characteristics are stabilized.
  • the average value of kurtosis Sku on the surface on the magnetic layer 43 side is 5.50 or less, preferably 3.30 to 5.50, more preferably 3.80 to 5.50, and even more preferably 3.80 to 4.80.
  • the average value of kurtosis Sku is 5.50 or less, the unevenness on the surface on the magnetic layer 43 side is prevented from becoming excessively sharp, and the protrusions 430 on the surface on the magnetic layer 43 side are less likely to be scraped off when the head unit 56 slides against the magnetic tape MT. Therefore, powder falling during recording or reproduction is suppressed.
  • the average value of kurtosis Sku is 3.30 or more, the contact area between the head unit 56 and the magnetic tape MT is reduced, and the dynamic friction coefficient during recording or reproduction is reduced.
  • the average value of the root mean square roughness Sq on the surface on the magnetic layer 43 side is preferably 2.25 nm or less, more preferably 2.20 nm or less, even more preferably 2.15 nm or less, 2.10 nm or less, 2.05 nm or less, or 2.01 nm or less.
  • the average value of kurtosis Sku and the average value of root-mean-square roughness Sq on the surface on the magnetic layer 43 side can be calculated as follows:
  • the kurtosis Sku and root mean square roughness Sq of the two-dimensional surface profile image are measured using image analysis software (SPIP (registered trademark) version 6.7.3, manufactured by Image Metrology, Inc.) as follows.
  • SPIP registered trademark
  • the image analysis software open the two-dimensional surface profile image to be analyzed.
  • Select Sa analysis from the Analysis tab open the Roughness & Texture Analysis window, and set the Input Window and Parameters in the window as follows.
  • Plane Correction Selection Substract Plane Parameters SPIP Classic selected Plug-in Parameters not selected
  • the six kurtosis Sku values obtained from each of the six two-dimensional surface profile images are simply averaged (arithmetic mean) to calculate the average kurtosis Sku value.
  • the six root-mean-square roughness Sq values obtained from each of the six two-dimensional surface profile images are simply averaged (arithmetic mean) to calculate the average root-mean-square roughness Sq value.
  • Fig. 10 is a diagram for explaining the relationship between the unevenness on the surface on the magnetic layer 43 side, the ratio of the integrated values of PSD I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 , and kurtosis Sku.
  • the uneven shapes (1) to (5) shown in Fig. 10 show an image of the unevenness on the surface on the magnetic layer 43 side. Note that Fig. 10 is merely an image of the unevenness, and does not accurately represent the unevenness of the actual magnetic tape MT.
  • the ratio of the integrated values of the PSD I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 decreases in the order from the concave-convex shape (1) to the concave-convex shape (5).
  • the kurtosis Sku does not decrease in the order from the concave-convex shape (1) to the concave-convex shape (5). Therefore, there is no correlation between the ratio of the integrated values of the PSD I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 and the kurtosis Sku.
  • the ratio of the integrated values of the PSD I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 is large, whereas the kurtosis Sku is small. In this case, although it is possible to suppress the occurrence of powder falling during recording or reproduction, there is a risk that excellent electromagnetic conversion characteristics cannot be obtained.
  • the ratio of the integrated values of the PSD I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 is small, while the kurtosis Sku is large. In this case, excellent electromagnetic conversion characteristics are obtained, but there is a risk of powder falling during recording or reproduction.
  • the paint for forming the undercoat layer is prepared by kneading and dispersing the non-magnetic particles and the binder in the solvent.
  • the paint for forming the magnetic layer is prepared by kneading and dispersing the magnetic particles and the binder in the solvent.
  • the following solvents, dispersing devices, and kneading devices can be used to prepare the paint for forming the magnetic layer and the paint for forming the undercoat layer.
  • Solvents used in preparing the above-mentioned paints include, for example, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol-based solvents such as methanol, ethanol, and propanol; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether-based solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene; and halogenated hydrocarbon-based solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. These may be used alone or
  • the kneading device used in the above-mentioned paint preparation may be, for example, a continuous twin-screw kneader, a continuous twin-screw kneader capable of dilution in multiple stages, a kneader, a pressure kneader, a roll kneader, etc., but is not limited to these devices.
  • the dispersing device used in the above-mentioned paint preparation may be, for example, a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, the "DCP Mill” manufactured by Eirich), a homogenizer, an ultrasonic dispersing machine, etc., but is not limited to these devices.
  • a coating material for forming a base layer is applied to one main surface of the substrate 41 and dried to form a base layer 42.
  • a coating material for forming a magnetic layer is applied to the base layer 42 and dried to form a magnetic layer 43 on the base layer 42.
  • the magnetic particles are magnetically oriented in the thickness direction of the substrate 41, for example, by a solenoid coil. Also, during drying, the magnetic particles may be magnetically oriented in the running direction (longitudinal direction) of the substrate 41, and then magnetically oriented in the thickness direction of the substrate 41, for example, by a solenoid coil.
  • the degree of vertical orientation of the magnetic particles i.e., the squareness ratio S1
  • the degree of vertical orientation of the magnetic particles i.e., the squareness ratio S1
  • a back layer 44 is formed on the other main surface of the substrate 41. This results in a magnetic tape MT.
  • the squareness ratios S1 and S2 are set to the desired values by, for example, adjusting the strength of the magnetic field applied to the coating film of the magnetic layer-forming paint, the concentration of the solids in the magnetic layer-forming paint, and the drying conditions (drying temperature and drying time) of the coating film of the magnetic layer-forming paint.
  • the strength of the magnetic field applied to the coating film is preferably two to three times the coercive force of the magnetic particles.
  • the magnetic tape MT is wound into a roll, and then the magnetic tape MT is subjected to a heat treatment in this state to harden the underlayer 42 and the magnetic layer 43 .
  • the magnetic tape MT may be demagnetized and then a servo pattern may be written onto the magnetic tape MT.
  • the magnetic tape MT is cut to a predetermined width (for example, 1/2 inch width). In this manner, the magnetic tape MT is obtained.
  • the ratio of integrated values of PSD I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 , kurtosis Sku, and root-mean-square roughness Sq can be adjusted to desired values, for example, by adjusting the particle size and amount of inorganic additives added to the magnetic layer forming paint, adjusting the conditions of the calendaring process, and adjusting the thickness of the undercoat layer 42 and the magnetic layer 43.
  • the inorganic additives include inorganic particles such as carbon particles, abrasive particles such as alumina particles, etc.
  • the conditions of the calendaring process include the temperature and pressure of the calendaring process.
  • the ratio I ⁇ n ⁇ 5 /I 10 ⁇ ⁇ n ⁇ 20 of the average value I ⁇ n ⁇ 5 ⁇ m of the integrated value of PSD to the average value I 10 ⁇ ⁇ n ⁇ 20 ⁇ m of the integrated value of PSD is 3.00 or less. This allows the spacing amount that affects the electromagnetic conversion characteristics to be set to a preferred amount. Therefore, excellent electromagnetic conversion characteristics can be obtained.
  • the average value of kurtosis Sku on the surface on the magnetic layer 43 side is 5.50 or less. This makes it possible to prevent the protrusions 430 on the surface on the magnetic layer 43 side from being scraped off when the head unit 56 and the magnetic tape MT slide against each other. This makes it possible to prevent the occurrence of powder falling off during recording or playback. This makes it possible to prevent deterioration of the running properties of the magnetic tape MT (for example, increased friction between the head unit 56 and the magnetic tape MT, etc.).
  • the head unit 56 is maintained at an angle to the axis Ax parallel to the width direction of the magnetic tape MT when recording and reproducing the magnetic tape MT.
  • the protrusions 430 on the surface on the magnetic layer 43 side are easily scraped off during recording or reproduction, and the powder 57 is easily dropped off.
  • the head unit 56 is maintained at an angle to the axis Ax parallel to the width direction of the magnetic tape MT, the dropped powder 57 is easily spread over the entire surface of the head unit 56 as the magnetic tape MT runs, as shown in Fig. 12. For this reason, there is a risk that the friction between the magnetic tape MT and the head unit 56 increases during recording or reproduction, and the running stability decreases.
  • the average value of kurtosis Sku on the surface on the magnetic layer 43 side is 5.50 or less, so that scraping of the protrusions 430 on the surface on the magnetic layer 43 side is suppressed during recording or reproduction. Therefore, even if the head unit 56 is kept at an angle during recording or reproduction, an increase in friction between the magnetic tape MT and the head unit 56 can be suppressed, and a decrease in running stability can be suppressed.
  • the magnetic tape cartridge 10 is a one-reel type cartridge, but it may be a two-reel type cartridge.
  • Fig. 13 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 321.
  • the cartridge 321 comprises an upper half 302 made of synthetic resin, a transparent window member 323 that fits into and is fixed to a window portion 302a opened on the upper surface of the upper half 302, a reel holder 322 that is fixed to the inside of the upper half 302 and prevents the reels 306 and 307 from floating up, a lower half 305 that corresponds to the upper half 302, the reels 306 and 307 that are stored in the space formed by combining the upper half 302 and the lower half 305, the magnetic tape MT wound on the reels 306 and 307, a front lid 309 that closes the front opening formed by combining the upper half 302 and the lower half 305, and a back lid 309A that protects the magnetic tape MT exposed at this front opening.
  • Reels 306 and 307 are used to wind magnetic tape MT.
  • Reel 306 comprises a lower flange 306b having a cylindrical hub portion 306a in the center around which magnetic tape MT is wound, an upper flange 306c of approximately the same size as lower flange 306b, and a reel plate 311 sandwiched between hub portion 306a and upper flange 306c.
  • Reel 307 has the same configuration as reel 306.
  • the window member 323 has mounting holes 323a at positions corresponding to the reels 306 and 307 for attaching reel holders 322, which are reel holding means for preventing the reels from floating up.
  • the magnetic tape MT is the same as the magnetic tape MT in the first embodiment.
  • the average aspect ratio of magnetic particles, the average particle volume of magnetic particles, the average thickness of the magnetic tape, the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the back layer, the average value I ⁇ n ⁇ 5 of the integrated value of PSD in the range of spatial wavelength ⁇ n ⁇ 5 ⁇ m, the average value I ⁇ n ⁇ 20 of the integrated value of PSD in the range of 10 ⁇ m ⁇ spatial wavelength ⁇ n ⁇ 20 ⁇ m, the ratio of the integrated values of PSD I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 , kurtosis Sku, root mean square roughness Sq, the squareness ratio S1 of the magnetic layer in the perpendicular direction of the magnetic tape, and the squareness ratio S2 of the magnetic layer in the longitudinal direction of the magnetic tape are values obtained by the measurement method described in the above embodiment.
  • Example 1 (Preparation process of paint for forming magnetic layer)
  • the magnetic layer coating material was prepared as follows. First, the first composition having the following composition was mixed with an extruder. Next, the mixed first composition and the second composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Then, further mixing was performed with a dyno mill and filtering was performed to prepare the magnetic layer coating material.
  • Aluminum oxide powder 3 parts by mass ( ⁇ -Al 2 O 3 , average particle size 0.1 ⁇ m)
  • the paint for forming the undercoat layer was prepared as follows. First, the third composition having the following composition was mixed with an extruder. Next, the mixed third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Then, further mixing was performed with a dyno mill and filtering was performed to prepare the paint for forming the undercoat layer.
  • Carbon black 25 parts by mass (manufactured by Asahi Carbon Co., Ltd., product name: #80)
  • n-Butyl stearate 2 parts by weight Methyl ethyl ketone: 130 parts by weight Toluene: 75 parts by weight Cyclohexanone: 80 parts by weight
  • the coating material for forming the back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and the mixture was filtered to prepare the coating material for forming the back layer.
  • Carbon black manufactured by Asahi Carbon Co., Ltd., product name: #80
  • Polyester polyurethane manufactured by Nippon Polyurethane Co., Ltd., product name: N-2304
  • Methyl ethyl ketone 500 parts by weight
  • Toluene 400 parts by weight
  • Cyclohexanone 100 parts by weight
  • Polyisocyanate manufactured by Tosoh Corporation, product name: Coronate L
  • PEN film long polyethylene naphthalate film
  • base film non-magnetic support
  • the magnetic particles were magnetically oriented in the thickness direction of the film by a solenoid coil.
  • the squareness ratio S1 in the perpendicular direction (thickness direction) of the magnetic tape was set to 65%
  • the squareness ratio S2 in the longitudinal direction of the magnetic tape was set to 38%.
  • a paint for forming a back layer was applied to the other main surface of the PEN film and dried to form a back layer with an average thickness of 0.30 ⁇ m after calendaring. This resulted in a magnetic tape.
  • the magnetic tape was wound into a roll, and then in this state, it was subjected to a heat treatment at 70° C. for 48 hours to harden the underlayer and the magnetic layer.
  • Servo pattern writing process After the cut magnetic tape was demagnetized, a servo pattern was written on the magnetic tape using a servo writer to form five servo bands. The servo pattern was made to conform to the LTO-8 standard. In this manner, the desired magnetic tape was obtained.
  • Example 2 A magnetic tape having various surface parameters shown in Table 1 was obtained in the same manner as in Example 1, except that in the preparation process of the paint for forming the magnetic layer, the amount of carbon black in the second composition was changed from 1 part by mass to 0.6 parts by mass.
  • Example 3 A magnetic tape having various surface parameters shown in Table 1 was obtained in the same manner as in Example 1, except that in the preparation process of the coating material for forming the magnetic layer, the amount of aluminum oxide powder in the first composition was changed from 3 parts by mass to 5 parts by mass, and the amount of carbon black in the second composition was changed from 1 part by mass to 2 parts by mass.
  • Example 1 In the preparation process of the coating material for forming the magnetic layer, the amount of aluminum oxide powder in the first composition was changed from 3 parts by mass to 7.5 parts by mass, and the amount of carbon black in the second composition was changed from 1 part by mass to 2.5 parts by mass. Except for this, a magnetic tape was obtained in the same manner as in Example 1, with various surface parameters having the values shown in Table 1.
  • Example 2 A magnetic tape having various surface parameters shown in Table 1 was obtained in the same manner as in Example 1, except that in the preparation process of the paint for forming the magnetic layer, the arithmetic mean particle diameter of the carbon black in the second composition was changed from 70 nm to 50 nm, and the amount of carbon black in the second composition was changed from 1 part by mass to 1.5 parts by mass.
  • Example 4 A magnetic tape having various surface parameters shown in Table 1 was obtained in the same manner as in Example 1, except that the calendering temperature was lowered by 10° C. in the calendering step.
  • the peak of the captured spectrum was then taken as the signal amount S, and the floor noise excluding the peak was integrated from 3 MHz to 20 MHz to obtain the noise amount N.
  • the ratio S/N of the signal amount S to the noise amount N was calculated as the SNR (Signal-to-Noise Ratio).
  • the calculated SNR was then converted into a relative value (dB) based on the SNR of Comparative Example 4 as the reference media. The results are shown in Table 1.
  • the evaluation results in Table 1 reveal the following.
  • the ratio I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 of the average integrated value of PSD in the range of spatial wavelength ⁇ n ⁇ 5 ⁇ m obtained by measuring the surface on the magnetic layer side with an AFM to the average integrated value of PSD in the range of 10 ⁇ m ⁇ spatial wavelength ⁇ n ⁇ 20 ⁇ m obtained by measuring the surface on the magnetic layer side with an AFM is 3.00 or less, an excellent SNR is obtained.
  • the average value of kurtosis Sku on the surface on the magnetic layer side is 5.50 or less, powder falling during data recording or the like can be suppressed.
  • Example 3 and Comparative Example 4 From the evaluation results of Example 3 and Comparative Example 4, it is found that an excellent SNR cannot be obtained simply by having a small I ⁇ n ⁇ 5 , but an excellent SNR can be obtained by setting the ratio I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 to 3.00 or less. From the evaluation results of Example 1 and Comparative Example 4, it can be seen that a small Ra alone does not result in an excellent SNR, and that an excellent SNR can be obtained by setting the ratio I ⁇ n ⁇ 5 /I 10 ⁇ n ⁇ 20 to 3.00 or less.
  • the present disclosure may also employ the following configuration.
  • a tape-shaped magnetic recording medium, A substrate and a magnetic layer are provided,
  • the average thickness of the magnetic recording medium is 5.30 ⁇ m or less;
  • the ratio I ⁇ n ⁇ 5 / I 10 ⁇ n ⁇ 20 is 2.80 or less; 1. A magnetic recording medium according to claim 1. (3) The ratio I ⁇ n ⁇ 5 / I 10 ⁇ n ⁇ 20 is 2.10 or less; 1. A magnetic recording medium according to claim 1. (4) The average value I ⁇ n ⁇ 5 of the integrated value is 2.20 nm2 or less; The magnetic recording medium according to any one of (1) to (3). (5) The average value I 10 ⁇ n ⁇ 20 of the integrated values is 0.70 nm2 or less; The magnetic recording medium according to any one of (1) to (4). (6) The average value I 10 ⁇ n ⁇ 20 of the integrated values is 0.65 nm2 or more; The magnetic recording medium according to any one of (1) to (5).
  • the average value of kurtosis on the surface on the magnetic layer side is 3.30 or more and 5.50 or less;
  • the magnetic recording medium according to any one of (1) to (6). the average value of kurtosis on the surface on the magnetic layer side is 3.80 or more and 5.50 or less;
  • the magnetic recording medium according to any one of (1) to (6). (9) the average value of kurtosis on the surface on the magnetic layer side is 3.80 or more and 4.80 or less;
  • the magnetic recording medium according to any one of (1) to (6). (10) the average value of the root mean square roughness on the surface on the magnetic layer side is 2.25 nm or less;
  • the magnetic layer has a servo pattern; the servo pattern includes a plurality of first magnetized regions and a plurality of second magnetized regions; the plurality of first magnetized regions and the plurality of second magnetized regions are asymmetric with respect to an axis parallel to a width direction of the magnetic recording medium;
  • the magnetic recording medium according to any one of (1) to (10).
  • (12) a tilt angle of the first magnetization region with respect to the axis and a tilt angle of the second magnetization region with respect to the axis are different, the larger of the inclination angle of the first magnetization region and the inclination angle of the second magnetization region is equal to or greater than 18° and equal to or less than 28°;
  • the magnetic layer is configured to be capable of recording signals with a data track width of 850 nm or less and a bit length of 47 nm or less;
  • (14) Further comprising a base layer;
  • the average thickness of the underlayer is 0.90 ⁇ m or less.
  • (15) The average thickness of the magnetic layer is 0.08 ⁇ m or less.
  • the average thickness of the substrate is 4.40 ⁇ m or less.
  • the magnetic layer includes magnetic particles;
  • the average particle volume of the magnetic particles is 1500 nm3 or less;
  • the magnetic layer includes magnetic particles;
  • the magnetic particles include hexagonal ferrite, ⁇ iron oxide, or Co-containing spinel ferrite;
  • a tape-shaped magnetic recording medium, A substrate and a magnetic layer are provided,

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  • Magnetic Record Carriers (AREA)
PCT/JP2023/037983 2022-10-26 2023-10-20 磁気記録媒体およびカートリッジ Ceased WO2024090340A1 (ja)

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JP2022-171754 2022-10-26
JP2022171754 2022-10-26

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